Accurate temperature control of a small, heated probe is required in many different environments. For example, in the surface mount technology of electronic chips, there is a need to solder very tiny leads onto boards without damaging the components or the narrow leads of the printed circuit board. The temperature of the soldering tip must be above a selected temperature but must not exceed a certain temperature range for a period of time. In dentistry, narrow, heated probes are used in root canal therapy when filling the root system with heat-softened gutta percha (natural rubber) or other substances. Heated tips are often used to cauterize blood vessels to prevent bleeding. The tips are frequently very small and require precise temperature control at the point of application.
Current technology suffers from significant constraints making it very difficult to develop a suitable miniature, heated probe that is temperature-controlled.
A heated medical or dental probe of this type is shown and described in U.S. Pat. No. 4,527,560 to the same inventor of the present application and is incorporated herein by reference.
Traditionally, a soldering iron includes a relatively large thermostatically controlled tip made from a material of good heat conductivity, usually copper. This tip acts as a heat reservoir from which the heat is conducted to a narrow soldering point. However, if this point becomes too narrow, it is mechanically weak and in addition tends to be easily destroyed by oxidation. At the same time, the amount of heat which can be conducted to the tip decreases the narrower the tip becomes. For these and other reasons, accurate measurement of the temperature of the tip and maintaining the temperature within a precise range is not possible with current technology.
U.S. Pat. No. 4,074,719, in columns 5 and 6 and FIG. 3, describes a device for causing blood coagulation. A thermocouple within the heating probe provides a voltage for determining the temperature. The probe of the prior art does not include a switch to switch the probe between the power supply and the thermocouple voltage sensor.